Invasive Lespedeza cuneata and native Lespedeza virginica experience asymmetrical benefits from rhizobial symbionts

BACKGROUND AND AIMS: Lespedeza cuneata (Dum. Cours.) G. Don is an invasive legume that displaces populations of native N. American congeners. Our aims are to determine the growth benefits of different rhizobacterial strains for L. cuneata and native Lespedeza virginica (L.) Britton, and to determine if these strains influence competition between these plants. METHODS: Plants were grown under nitrogen-limiting conditions in sterilized soil in pairs consisting of two L. cuneata, two L. virginica, or one of each species, and then plants were inoculated with one of seven rhizobial isolates, or with a no-strain control. After 3 months, plants were harvested for determination of biomass and nodulation rate. RESULTS: Five of the assayed stains improved L. cuneata biomass over uninoculated controls, but none of the strains benefited L. virginica. L. cuneata plants had more biomass and root nodules when grown in competition with L. virginica than with a conspecific. CONCLUSIONS: Asymmetrical benefits from these symbionts accrued to invasive L. cuneata but not to native L. virginica, and this may provide the invader with a growth advantage in the field. Changes in the availability of effective symbionts in the soils of invaded sites can shape performance of native and invasive plants.